juice to its sailors to prevent scurvy. (This is the origin of the slang word “limey” for
the British.) The use of fish-liver oils for the treatment of rickets (later recognized as
vitamin D deficiency), a bone-growth disorder, has been known since the nineteenth
century. These uses all predate the recognition of the essential function of these sub-
stances and the term “vitamine,” coined by Funk in 1912.
On the basis of their solubility and polarity, vitamins are divided into two categories:
the water-soluble and the fat-soluble vitamins. The former cannot be stored in any bio-
compartment and must be ingested regularly. In that context, it is important to caution
about the many and periodically recurring fads and myths embraced by the lay public and
press. Since vitamins are widely known but misunderstood, there is a need to educate the
public about their misuse, as well as in other areas of pseudoscientific misunderstanding.
8.2.8.1 Vitamin B 1 (Thiamine)
Vitamin B 1 (8.43, thiamine) is a pyrimidinyl methyl thiazolium derivative that occurs in
bran (mostly rice hulk), beans, nuts, egg yolk, yeast, and vegetables. In its pyrophos-
phate form it is a coenzyme of pyruvate dehydrogenase, which oxidatively decarboxy-
lates pyruvate to form acetyl-coenzyme A. Consequently, it is a very important
coenzyme, catalyzing the connecting step between glycolysis and the Krebs cycle. The
carbon between the sulfur and nitrogen of the thiazole ring of the vitamin is very acidic
and adds to the carbonyl of pyruvate, leading to decarboxylation. Thiamine is also a
coenzyme of transketolase, which transfers two-carbon fragments between carbohy-
drates in the pentose phosphate pathway (pentose shunt), a multipurpose metabolic
reaction sequence.
Vitamin B 1 deficiency, known as beriberi,was historically seen primarily in people
of southeast Asia, for dietary reasons. The symptoms of beriberi are neurological dis-
orders (weakness, paralysis, painful neuritis), diarrhea, loss of appetite, dermatitis, and
anemia. These symptoms are due mainly to the accumulation of pyruvate and lactate.
Some analogs of thiamine are biologically active, but have not attained wide use
because thiamine itself is cheaply available.
8.2.8.2 Vitamin B 2 (Riboflavin)
Vitamin B 2 (8.44, riboflavin) is a benzopteridine derivative carrying a ribityl (reduced
ribose) side chain. It occurs in almost all foods, the largest amounts being found in eggs,
meat, spinach, liver, yeast, and milk. Riboflavin is one of the major electron carriers as
a component of flavine-adenine dinucleotide (FAD), which is involved in carbohydrate
and fatty acid metabolism. A hydride ion and a proton are added to the pyrazine ring of
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